Apparatus, method and program for image processing, and display device

ABSTRACT

An image processing apparatus sequentially provides a display device with a plurality of image output including a first image, a second image set to become at least a part of an image that is not correlated with the first image when luminance values of pixels of the first image are added to it, and a third image set to become an image, which is obtained by adding luminance values of pixels of all pluralities of images, higher spatial-frequency components than those of the first image. The image processing apparatus has an optical shutter control unit for controlling an optical shutter provided between the display device and a viewer to make the shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.

This application is a continuation of U.S. application Ser. No.12/601,779 filed Nov. 24, 2009, which is a National Stage ofInternational Application No. PCT/JP2008/59581, filed May 23, 2008,which claims priority from Japanese Patent Application No. 2007-139605,filed on May 25, 2007, the disclosures of which are incorporated hereinby reference in their entirety.

TECHNICAL FIELD

The present invention relates to an image processing apparatus, a methodand a program therefor, and a display device, and more particularly, toan apparatus capable of presenting a content to a specified user and anauthenticated person, and a method and a program therefor.

BACKGROUND ART

Flat panel displays, such as a liquid crystal display and a plasmadisplay, are applied in a wide range from mobile devices, such as aportable telephone, to large equipments, such as a public display. Mostof those displays are developed with a focus on a wide viewing angle,high brightness, and high image quality, being required to display animage with clearness and easy to be viewed at any angles.

Meanwhile, some contents shown on displays include confidentialinformation and private data which are not supposed to be viewed inpublic. Therefore, it is an important issue that a displayed content isprotected from general public viewing in a ubiquitous environment thathas been developed today along with development of information devices.Even in an office, there is a case where some confidential information,which needs to be protected against view by someone walking behind aseat, is handled.

Some portable telephones include a display with an optical maskingshield (a louver) so that a displayed content can be viewed only from aspecific direction. Even in such a case, the displayed content can beviewed by someone just behind a person handling it, and securityprotection is not sufficient.

As a technique to solve the above mentioned problem, there is an “imagedisplay device” disclosed in Patent Document 1. The image display devicepresents an image (hereinafter, referred to as a secret image) to aviewer wearing glasses with an image selecting function, and alsopresents another image (hereinafter, referred to as a public image) toother viewers.

Specifically, FIG. 11 shows an image display device, in which inputimage signals 11 are stored in an image data storage memory 12 with acapacity of signals for one frame, controlled by a frame signal 13, thenimage data in the image data storage memory 12 are read out at twice thespeed of frame period, and signals read out primarily are compressedinto a half size to become a first image signal 14 and are inputted intoa synthetic circuit 15. The secondly read-out image signals have theirchroma and luminance converted to become second image signals 17 andinputted into the synthetic circuit 15. Therefore, an image display 18shows the first image signals 14 and the second image signals 17alternately. Meanwhile, the frame signal 13 drives a shutter of glasses21 using a glasses shutter timing generation circuit 19 so that a viewercannot view an image depending on the second image signals 17. Accordingto such a configuration and operation, those who without glasses view agray image or a third image (a public image) which is a synthetic imageof the first image signals 14 and the second image signals 17, and whichhas no correlation with the first image signals; on the other hand,those who wear glasses can view a desired image (a secret image) basedon the first image signals.

Further, as another technique to solve the aforementioned problem, thereis a “Secure method for providing privately viewable data in a publiclyviewable display” disclosed in Patent Document 2. The method forproviding data capable of being viewed privately, disclosed in PatentDocument 2, allows only a permitted user (a viewer) to decipher aprivate image (a secret image) on a display, at the same time, thatallows an unpermitted user to simply view a random pattern, an imagedifficult to be deciphered, or may be a screen saver image (a publicimage). In order to promote the object above, an image processingtechnique including a data hiding pattern and an alternation pattern issynchronized with a display including an image made by an imageprocessing technology, that is, for example, combined with a wearabledevice such as active glasses. Finally, by a known ability of visualsystem of human for making a dissimilar image be merged into a singleimage, a performance can be complete in which data capable of beingviewed privately can be presented on a display viewed publicly.

Patent Document 1: Japanese Patent Application Laid-open No. 63-312788

Patent Document 2: Japanese Patent Application Laid-open No. 2001-255844

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, inventions disclosed in aforementioned Patent Documents 1 and 2have a case in which a content of the secret image may be deciphered.When a person without shutter glasses moves his/her gaze directionsuddenly, an image by the first image signal and an image by the secondimage signal are misaligned and an image contour of the secret image inthe synthetic image may be perceived. Such a phenomenon occurs even whena person without glasses moves his/her eyes without any intention due tohis/her blinking or the like.

Patent Document 2 has another disclosure in which division images,generated by dividing a secret image into a plurality of images, aredisplayed sequentially having a public image displayed therebetween, sothat the secret image, which is a synthetic image of division images, isprevented from being browsed. However, in this case, those who withoutshutter glasses can easily and instantaneously perceive a divisionpattern (which is a pattern generated when the secret image is dividedinto two division images, for example, by way of spatial division)because of their blinking, and the pattern becomes visually annoying.

An object of the present invention is to provide an apparatus, methodand program for image processing, and a display device, with whichstealing a glance at a secret image and visually annoying display,mentioned above, are restrained with a simple way.

Means for Solving the Problems

In order to achieve the aforementioned object, the image processingapparatus, according to the present invention, for outputting imagesignals of a plurality of images sequentially to a display device;wherein

-   -   a first image and a second image of the plurality of images are        in a relationship in which, when luminance values of pixels in        the respective images are added, an image having no correlation        with the first image is created, and the apparatus comprises:    -   a unit for setting a third image so that an image obtained by        adding luminance values of pixels in all outputted images        including the first and the second images becomes an image        including a lot of spatial-frequency components which are equal        to or higher than spatial-frequency components included in the        first image; and    -   an optical shutter control unit for controlling an optical        shutter provided between the display device and a viewer to make        the shutter be in a light transmission state while a part of or        all the first image is displayed, and in a light interception        state while other images are displayed.

According to the present invention, a third image (a public image) isset so that an image made by adding a plurality of displayed imageincluding the first image (a secret image) and the second image (areverse image, for example) at least a part of which is set to have nocorrelation with the first image becomes an image including a lot ofhigh spatial-frequency components, for example a geometric pattern withhigh contrast, that is highly visible. Then, the secret image becomesdifficult to be viewed. Thus, when a person without using shutterglasses views the image, it is difficult for him/her to perceive thesecret image intentionally or unintentionally. In addition, when thepublic image is set so that spatial-frequency characteristic of an imagemade by adding all images (including the first, second and third images)becomes similar to a spatial-frequency characteristic of the secretimage, a content of the secret image becomes more difficult to beperceived because of masking effect. Thus, the secret image can maintainhigher confidentiality against a viewer viewing the image directlywithout using the optical shutter. As described, a person withoutwearing shutter glasses is restrained from stealing a glance at a secretimage.

Advantageous Effect of the Invention

According to the present invention, a person viewing an image directlywithout using an optical shutter can be restrained from stealing aglance at the secret image with a simple method.

BEST MODE FOR CARRYING OUT THE INVENTION Principle of the Invention

Even with the aforementioned conventional arts, those who withoutwearing shutter glasses can perceive patterns of a secret image ordivision images without any intention. This perception is created whenthey intentionally blink at high speed, or when they simply blink duringtheir viewing. The perception is caused by such reasons that a secretimage fails to be canceled by time integration between a secret imageand a luminance reverse image in which each color component of thesecret image is reversed (hereinafter, referred to as a “reverseimage”), and conditions of a public image (a luminance value,spatial-frequency characteristic of the image) are in a state with whichthe secret image becomes easy to be perceived when the cancellation isnot performed well.

For example, as shown in FIG. 9( a), when a secret image is a checkeredpattern with black-white and a reverse image is a black-white reversedpattern, an uncorrelated image (a perceived image) becomes a solid imagehaving low spatial-frequency where entire tone is the same, and acontour of the checkered pattern can be perceived if a line-of-sightmoves instantaneously. Even if a third image (a public image) shown inFIG. 9( b) is added to the above, a person can perceive the checkeredpattern (the secret image) unintentionally when the public image is asolid image, by blinking his/her eyes, unless the secret image is muchdarker than the public image as shown in the figure.

If a public image gathers attention, it becomes hard for a secret imageto be caught relatively. Consequently, the perception mentioned abovecannot be achieved.

In the present invention, a public image is set to be an image capableof gathering attention easily, for example, a geometric image with highspatial-frequency and high contrast.

Specifically, a public image is constructed, as shown in FIG. 9( c),with high contrast components such as black and white, and is set to bean image having many contour parts in order to gather attention easily,that is, a geometric image with high spatial-frequency. Consequently, asecret image can hardly gather attention relatively and stealing aglance of the secret image can be restrained with the simple method.

Further, when a secret image includes characters as shown in FIG. 9( d),an uncorrelated image (the perceived image) becomes a solid image withlow spatial-frequency having the same tone entirely. Therefore, acontour part of the characters can be caught instantaneously whenline-of-sight moves, and the characters can be read.

As shown in FIG. 9( e), by setting a geometric pattern in a public imageto have a short-term cycle, that is, to have a high spatial-frequencycharacteristic, a content of the secret image can be less perceived bymasking effect, and therefore, the secret image can obtain higherconfidentiality. Especially, when a secret image contains characters,the character size and the cycle of the geometric pattern of the publicimage are made to be equivalent, that is, the spatial-frequencies of thesecret image and the public image are made to be same, so that thecharacters becomes difficult to be read.

In the above description, the case has been explained in which thefirst, second and third images are displayed independently, in atemporally sequential manner. However, there can be another case asshown in FIG. 9( f), where half luminance of the secret image, i.e.,(the first image)/2, and addition of each half luminance of the reverseand public images, i.e., (the second image+third images)/2, may be shownalternately. Moreover, (the first image)/2, (the second image+thirdimage)/2 and (the third image) may be displayed sequentially. In thatcase, luminance ratio of the first image (a secret image) to the thirdimage (a public image) becomes higher, and at the same time, contrastbecomes relatively high. Thus, stealing a glance at the secret image canbe prevented more effectively. In the above, all that required is thatthe secret image and the reverse image are in a relationship in whichthose are cancelled with each other by adding those luminance values,and the secret image is desirably darker than the public image, as longas it can be viewed.

There is another example with same spatial-frequencies. As shown in FIG.10( a), it is possible that the third image has characters in the samesize of those in the first image. In that case, it is essential thatcontents of those images are not correlated, and cannot be known byanalogy.

FIG. 10( b) shows a case in which a part of the first image is made tobe a secret image. The part to be secret is reversed in the secondimage, and a geometric pattern is provided in the third image. Then,equivalent effect can be obtained.

The above described restraint for perception of the secret image can bealso applied to a case of a pattern of division image shown in FIG. 10(c), naturally. In the figure, a checkered pattern of a public image isused as a division pattern, and a secret image is divided into two usingthe pattern. Reverse images are made by reversing respective divisionimages. Further, a character size is equivalent to a cycle of thegeometric pattern of the public image. As shown, a geometric pattern isset to be corresponding to each spatial-frequency characteristic of thedivision image pattern and the secret image that is a synthetic image ofdivision images. Thus, equivalent effect can be obtained, in which adivision image pattern is not eyesore and a content of secret image canbe hardly perceived.

The aforementioned is an example with a black-white image; however, thehigh contrast image can be applicable to a colored image, and it isequivalent to an image with excellent chromaticness.

According to the above description, when the aforementioned method isapplied to an apparatus described in the followings, a secret image canbe hardly browsed by those who view the displayed image without anoptical shutter, that is, for example, those who do not wear the shutterglasses, and the secret image can be displayed with highconfidentiality.

First, as an image processing device, the apparatus can achieve adisplay of a secret image with high confidentiality, by using a publicimage having a high contrast geometric pattern. Next, as a displaydevice, the apparatus can achieve a display of a secret image with highconfidentiality, by displaying a public image having high contrastgeometric pattern. Hereinafter, a preferred embodiment based on theabove principle will be explained.

First Embodiment

A first embodiment, to which this invention is preferably applied, willbe explained. FIG. 1 shows a configuration of an image display apparatusaccording to the present invention. This image processing apparatus is aspecific device for processes based on the principle of the presentinvention, and includes a memory 101 storing a secret image (a firstimage), a reverse image (a second image) and a public image (a thirdimage) inputted sequentially; a data allocation circuit 102 forallocating data so that a display device can display the secret image,the reverse image, and the public image outputted sequentially from thememory 101 according to a synchronization signal; and a shutter glassescontrol signal generation circuit 103 for controlling the shutterglasses to make them be in a light transmission state or a lightinterception state based on an inputted synchronization signal.

An output signal from the memory 101 is represented by reference numeral111, one from the data allocation circuit 102 is represented byreference numeral 112, and one from the shutter glasses control signalgeneration circuit 103 is represented by reference numeral 113.

The secret image, the reverse image, and the public image stored in thememory 101 are sent to the data allocation circuit 102. The dataallocation circuit 102 allocates data for outputting the secret, reverseand public images, at every period based on a synchronization signal,and outputs them to the display device.

FIG. 2 shows an example of a timing diagram for one frame period withrespect to the output signals 111, 112, 113. Processing in the dataallocation circuit 102 will be explained using the timing diagram. Inthe explanation, one frame is divided into six sub-frames, where thesecret image is displayed in two of those sub-frames, the reverse imagein other two of those, and the public image in remaining two of those.The number of sub-frames and allocation for each image can bearbitrarily configured, unless an image, obtained by the calculation ofluminance synthesis between a secret image display and a reverse imagedisplay, has correlation with the secret image.

The secret image, the reverse image, and the public image are inputtedto the data allocation circuit 102, and the data allocation circuit 102allocates data of the secret image into the terms Ton 1 and Ton 2, andallocates data of the reverse image and the public image into the termsToff 1 and Toff 2. In this case, the secret image S and the reverseimage R are set so that an image synthesized by calculation S+R at eachpixel is not correlated with the secret image. For example, when thesecret image is an image represented by reference numeral 121 shown inthe FIG. 2, in which white characters “ABCDEF” are illustrated on ablack background, the reverse image becomes an image represented byreference numeral 122 shown in FIG. 2.

In the term Ton 1, the data allocation circuit 102 sends grayscalevalues of the secret image S to each pixel on the screen of the displaydevice during a data writing period W. After that, the circuit 102maintains a light transmission state or a light interception state untila next period W.

The data allocation circuit 102 also allocates data of the reverse imageR and the public image P in the same sort of processes (a writingprocess and a light transmission state maintaining process) even in theterm Toff 1, and reproduces grayscales of each image.

Also, the data allocation circuit 102 allocates data of the secret imageS and the reveres image R in the same sort of processes in the term Ton2 and Toff 2, and re-creates grayscales of each image.

The signal 113 sent to the shutter glasses makes the glasses be in thelight transmission state in the term Ton 1 and Ton 2, and in the lightinterception state in the term Toff 1 and Toff 2. The signal 113 isgenerated in the shutter glasses control signal generation circuit 103based on a synchronization signal of a screen image.

As a result of the above processing, when the public image is ageometric image represented by reference numeral 123 in FIG. 2, forexample, a viewer without using the shutter glasses perceives the imagerepresented by reference numeral 124 in FIG. 2.

In the above, the data allocation circuit 102 outputs the secret imageS, the reverse image R, and the public image P during one frame period,and an outputting order is basically arbitrary in principle. Forexample, as shown in FIG. 3, even if the periods for R and P (a fourthsub-frame and a sixth sub-frame) in the timing diagram of FIG. 2 arereplaced, a viewer with shutter glasses and a viewer without shutterglasses perceive images with no difference. As in the same manner, orderof the secret image, the reverse image, and the public image may bebasically arbitrary as long as an output signal is generated in theshutter glasses control signal generation circuit 103 to make theshutter glasses be in the light transmission state during the secretimage S display period.

What is important in the above is a pattern of the public image. It isdesirable that the public image be a geometric pattern with highcontrast so that the secret image becomes difficult to be viewedrelatively.

The image shown in FIG. 2 is one example of patterns based on theprinciple of the present invention, where a high contrast patterncontinues in the entire face at a short cycle. When thespatial-frequency characteristic of this pattern and that of a secretimage are similar to each other, a content of the secret image becomesdifficult to be browsed because of masking effect. For example, a publicimage pattern is selected, in response to the spatial-frequency of asecret image, from some patterns that are previously stored in thememory. It is more effective that a secret image is divided into aplurality of blocks and a public image pattern having an optimalspatial-frequency is selected for each block.

As mentioned, by selecting a public image, a secret image with highconfidentiality can be displayed.

Second Embodiment

A second embodiment, to which the present invention is preferablyapplied, will be explained. A configuration of an image processingapparatus according to the present embodiment is almost the same as thatof the image processing apparatus of the first embodiment; however, theapparatus according to the present embodiment includes a reverse imagegeneration section, and that is a different point from the apparatus ofthe first embodiment. FIG. 4 shows the configuration of the imageprocessing apparatus according to the present invention. The reverseimage generation section 104 inputs a secret image from the memory 101,and outputs a reverse image.

The reverse image generation section 104 generates a value (such as agrayscale value) for a reverse image to cancel a secret image, where thevalue is corresponding to a luminance value equivalent to a luminancevalue of “white” display of the secret image made by addition of thesecret image and the reverse image. The reason for the above is that animage is perceived on a retina by integrating luminance, not grayscale.

If such a reverse image is generated, the memory does not need to storereverse images, and can be in less size.

According to the aforementioned configuration, an equivalent effect ofthe first embodiment can be achieved, while an amount of image data tobe stored in the memory can reduced.

Third Embodiment

A third embodiment, to which the present invention is preferablyapplied, will be explained. An image processing apparatus according tothe present embodiment has the almost same configuration as that of thefirst embodiment; however, the apparatus according to the presentembodiment includes a public image generation section, and that is adifferent point from the first embodiment. FIG. 5 shows theconfiguration of the image processing apparatus according to the presentembodiment. The public image generation unit 107 inputs a controlsignal, which is a synchronization signal and the like, and outputs apublic image.

The public image generation section 107 outputs a geometric pattern inresponse to a control signal such as a synchronization signal. Forexample, to create a checkered pattern with eight-pixel cycle, an X-Ycoordinate of the image is obtained using the synchronization signal,and white is displayed when Xm, a reminder of X divided by 8, and Ym, areminder of Y divided by 8, are Xm<4 and Ym<4, or Xm>3 and Ym>3, andblack is displayed with any other cases. Therefore, the checkeredpattern can be obtained according to calculation. Of course, anypatterns other than the checkered pattern may be outputted arbitrary, ora public image may be generated by adding a control signal forinformation indicating a spatial-frequency characteristic based on asecret image pattern.

According to the aforementioned configuration, an equivalent effect ofthe first embodiment can be achieved, while an amount of image data tobe stored in the memory can reduced.

Fourth Embodiment

A fourth embodiment, to which the present invention is preferablyapplied, will be explained. FIG. 6 shows a configuration of a displaydevice according to the present invention. There is no limitation forthe display device, so it may be a plasma display, a display using anMEMS switch, an organic electroluminescence display, a high-speed liquidcrystal display, and the like.

This display device is a specific device for processing based on theprinciple of the present invention, and includes a memory 201 forstoring a secret image, a reverse image and a public image inputtedsequentially; a display controller 205 for setting display order to beoutputted to the display device, according to a synchronization signal,for the secret image, the reverse image and the public image, which areoutputted sequentially according to the synchronization signal from thememory 201, and for generating a control signal and an image signal fordriving the display device; a shutter glasses control signal generationcircuit 203 for controlling shutter glasses to make them be in a lighttransmission state or a light interception state; and a display section206.

As shown in the present embodiment, the display controller 205 includesthe processing of the data allocation circuit 102 of the firstembodiment, and the display device can realize an equivalent effect ofthe image processing apparatus. The display controller 205 may alsoinclude the processing of the reverse image generation section 104 ofthe second embodiment or the processing of the public image generationsection 107 of the third embodiment.

According to the aforementioned configuration, display of a secret imagecan be achieved with high confidentiality.

Fifth Embodiment

A fifth embodiment, to which the present invention is preferablyapplied, will be explained. Image processing of the present inventioncan be conducted as software processing using a computer. That meansthat an image processing section 131 is practically configured bysoftware in a computer, as shown in FIG. 7.

FIG. 8 shows a flow of an image processing method in the imageprocessing section 131 according to the present embodiment. When asecret image Sin and a reverse image Rin are inputted, in which both are8-bit raster images, a public image is generated inside the device, andimage display order and a glasses state of light transmission or lightinterception are set, with the image processing method. Steps S2 to S5are processing in the secret image generation section 107, Steps S6 andS7 are processing in the data allocation circuit 102, and Steps S8 toS10 are processing in the shutter glasses control signal generationcircuit 103.

The secret image Sin and the reverse image Rin (8 bit) are inputted intothe image processing section 131 (Step S1).

Public Image Generation Processing

The image processing section 131 extracts information indicating that towhich pixel the inputted image signal corresponds (that is, an X-Ycoordinate of the pixel) (Step S2).

Next, the image processing section 131 determines whether both of areminder of the X value of the pixel divided by 8 and a reminder of theY value of the pixel divided by 8 are smaller than 4, or bigger than 3(Step S3), and when the determined value is true, a value of 255 (whichis “white”) is selected as a value of the public image P (Step S4), andwhen the determined value is false, a value of 0 (which is “black”) isselected as a value of the public image P (Step S5).

Data Allocation Processing

In this case, one frame will be divided into 6 sub-frames (Step S6), inthe same manner as the case in the third embodiment. The imageprocessing section 131 selects and outputs an image in response to theorder of a sub-frame to which the image is going to be outputted.Specifically, the image processing section 131 selects Sin for a firstsub-frame, Rin for a second one, P for a third one, P for a fourth one,Sin for a fifth one, and Rin for a sixth one. The secret images areoutputted so as not to be adjacent to each other (Step S7). The imageprocessing section 131 also makes an image resulted by luminanceaddition Sin+Rin at every pixel be no correlated with the secret image.

Shutter Control Signal Generation Processing

The image processing section 131 checks whether the selected image isthe secret image or not (Step S8), and when it is the secret image, thesection outputs a control signal to make the shutter be in the lighttransmission state (Step S9), and when it is not, the section outputs acontrol signal to make the shutter be in the light interception state(Step S10).

As above, if software makes a computer execute the processing of theimage processing section 131 shown from Steps S1 to S10, an imageprocessing equivalent to that executed by the image processing apparatusaccording to the third embodiment can be executed without a specifichardware.

The flowchart shown in FIG. 8 is about an image processing equivalent tothat executed by the image processing apparatus according to the thirdembodiment of the present invention. In addition, software can also makea computer execute an image processing equivalent to that executed inthe first and the second embodiments of the present invention. When thesoftware processing is built up as a program, the program is recorded ona recording medium and becomes a target for business transaction.

Each of the above embodiments is an example of preferred embodiments,and the present invention is not limited to those.

For example, the above embodiments do not have specific descriptionabout respective RGB signals; however, if the embodiments are conductedwith respect to each of the signal components, the effect of the presentinvention can be also achieved for a colored image.

In addition, a raster image does not need to be a colored imageincluding a plurality of image signals, it may be a monochromatic image.That is, it is not necessary that the configurations shown in the aboveembodiments are provided for each color in parallel.

Further, the shutter glasses are used for perceiving a secret image inthe above; however, the configuration is not limited to using theglasses. Any configuration can be applicable as long as a shutter isprovided between a display and eyes.

Moreover, the present embodiments uses a secret image for explaining thepresent invention; however, an equivalent effect can be achieved withthe present invention even for a content and a pattern of divisionimages of a secret image with the same configuration.

As described, the present invention is capable of having variouschanges.

Aforementioned, the present invention has been explained with referenceto the embodiments (and examples), however, the present invention is notlimited to the above embodiments (and examples). Configurations anddetails of the present invention can be modified within the scope of theinvention, as long as those skilled in the art can understand themodification.

This application claims priority based on the Japanese PatentApplication No. 2007-139605, filed on May 25, 2007, and the entiredisclosures of which are hereby incorporated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of an image processingapparatus according to a first embodiment to which the present inventionis preferably applied;

FIG. 2 is a diagram showing an example of a timing diagram for eachcontrol signal in the image processing apparatus according to the firstembodiment;

FIG. 3 is a diagram showing another example of a timing diagram for eachcontrol signal in the image processing apparatus according to the firstembodiment;

FIG. 4 is a diagram showing a configuration of an image processingapparatus according to a second embodiment to which the presentinvention is preferably applied;

FIG. 5 is a diagram showing a configuration of an image processingapparatus according to a third embodiment to which the present inventionis preferably applied;

FIG. 6 is a diagram showing a configuration of a display deviceaccording to a fourth embodiment to which the present invention ispreferably applied;

FIG. 7 is a diagram showing a configuration of an apparatus forperforming an image processing method according to a fifth embodiment towhich the present invention is preferably applied;

FIG. 8 is a flowchart showing a flow of processing in the imageprocessing method according to the fifth embodiment;

FIGS. 9( a) to 9(f) are diagrams explaining a principle of the presentinvention;

FIGS. 10( a) to 10(c) are diagrams explaining a principle of the presentinvention; and

FIG. 11 is a diagram showing a configuration of an image processingdevice according to an art in a multipurpose type.

REFERENCE NUMERALS

101 Memory

102 Data allocation circuit

103 Shutter glasses control signal generation circuit

104 Reverse image generation section

105 Display controller

106 Display section

107 Public image generation section

111 Output signal from memory 101

112 Output signal from data allocation circuit 102

113 Output signal from shutter glasses control signal generation circuit103

131 Image processing section

201 Memory

202 Display controller

203 Shutter glasses control signal generation circuit

206 Display section

1. An image processing apparatus for outputting image signals of a plurality of images sequentially to a display device, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created; and wherein: the first image includes division images generated by diving the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, the image processing apparatus comprising: a unit for setting the third image so that the image obtained by adding luminance values of pixels of all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; and an optical shutter control unit for controlling an optical shutter provided between the display device and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.
 2. An image processing method for outputting image signals of a plurality of images sequentially to a display device, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images in the plurality of images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created, and wherein: the first image includes division images generated by dividing the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, the method comprising: setting the third image so that the image obtained by adding luminance values of pixels of all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; and controlling an optical shutter provided between the display device and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.
 3. A computer readable recording medium storing an image processing program for controlling image signals of a plurality of images and for outputting the image signals sequentially to a display device, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created, wherein: the first image includes division images generated by dividing the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, and the image processing program makes a computer execute the functions of: setting the third image so that the image obtained by adding luminance values of pixels in all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; and controlling an optical shutter provided between the display device and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.
 4. A display device for displaying sequentially image signals of a plurality of images, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created, wherein: the first image includes division images generated by dividing the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, and the device comprising: a unit for setting the third image so that the image obtained by adding luminance values of pixels in all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; and an optical shutter control unit for controlling an optical shutter provided between the display device and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.
 5. An image processor for outputting image signals of a plurality of images sequentially to a display device, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created, wherein: the first image includes division images generated by dividing the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, and the image processor comprising: a unit for setting the third image so that the image obtained by adding luminance values of pixels of all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; and an optical shutter controller for controlling an optical shutter provided between the display device and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed.
 6. A display for displaying sequentially image signals of a plurality of images, wherein the plurality of images includes a first image, a second image and a third image, and the first and the second images are in a relationship in which, when luminance values of pixels in the respective first and second images are added, an image having no correlation with the first image is created, wherein: the first image includes division images generated by dividing the first image into a plurality of images, and the third image is a public image viewed by unspecified viewers, and the display comprising: a unit for setting the third image so that the image obtained by adding luminance values of pixels in all output images including the first and the second images becomes an image including a lot of spatial-frequency components which are equal to or higher than spatial-frequency components included in a division pattern used in generating the division images; an optical shutter controller for controlling an optical shutter provided between the display and a viewer to make the optical shutter be in a light transmission state while a part of or all the first image is displayed, and in a light interception state while other images are displayed. 